During the drilling, completion, and production phases of wells for petroleum, the downhole use of compositions having certain rheology (e.g., pseudoplastic rheology) is important for a wide variety of purposes. Such fluids can more effectively carry materials (e.g., proppants) to a desired location downhole. Similarly, such fluids can more effectively carry materials away from a drilling location downhole. Further, the use of such fluids during hydraulic fracturing generally results in larger, more dominant fractures. Such fluids are sometimes prepared using agents that may have an appreciable water solubility and toxicity, such that it could have a deleterious effect if ingested by organisms (e.g., humans) upon unintended exposure to such compounds.